1. Technical Field of the Invention
The present invention relates to formation of a pad for external connection in a semiconductor device, and more particularly, to an electrode pad in a semiconductor device to which a bonding wire is connected, and a method of producing the same.
2. Description of the Related Art
Regarding pads for external connection in semiconductor devices, an appropriate material needs to be selected for a wiring member, and an adequate size must be ensured so that electrical connection of bonding wires, bumps, or the like become highly stable, and moreover, the resistance is prevented from increasing. Furthermore, to prevent the pads from peeling off which may be caused by different types of stresses and impacts, the pads need to be formed using a material having a high adhesion property for an insulation layer as a base.
FIG. 3 is a cross-sectional view showing the configuration of a conventional electrode pad in a semiconductor device. Generally, the layer structure of a pad wiring connected to an internal conductive region not shown in the drawing is formed on an interlayer insulation film 30 comprising, e.g., a BPSG (boron-phosphorus silicide glass) film, an SiO2 film, or the like and also, formed in an opening portion of the uppermost layer made of a passivation film 34.
Referring to an aluminum layer 33, a laminate comprising a Ti layer 31 and a TiN layer 32 as barrier metals is formed on the interlayer insulation film 30, and the layer 33 substantially made of aluminum is formed thereon. For example, the aluminum layer 33 has an AlCu structure which contains less than 1% of Cu (e.g., 0.5%).
For example, a bonding wire not shown in the drawing is connected to the electrode pad PAD comprising the aluminum layer 33 formed in the opening portion of the passivation film 34. The laminate comprising the Ti layer 31 and the TiN layer 32 is provided considering their adhesion properties and barrier properties for the base. The TiN layer 32 has a function of suppressing the Al of the aluminum layer 33 and the Si of an element from reacting with each other. Regarding the aluminum layer 33 and the Ti layer 31, reaction between the Al and the Ti is inhibited by the TiN layer 32 provided between them.
However, it is known that in the above-described configuration, the interlayer insulation film 30 made of an SiO2 film or the like as the base and the Ti layer 31 react with each other to form a TiO2 layer, which deteriorates the adhesion between them. Thus, in some cases, the Ti layer 31 and the TiN layer 32 are eliminated from the pad portion as a countermeasure for avoiding the configuration by which the strength of the pad is reduced. However, this countermeasure, that is, elimination of the barrier metals, is made only from the standpoint of the adhesion between the layers. Thus, there remains a danger that the bonding wire is released (reduction of the bond-lift strength).
In view of the above-described situations, the present invention has been devised, and an object of the present invention is to provide an electrode pad in a semiconductor device in which a countermeasure against the bond-lift defect on the pad surface is taken, and a method of producing the same.
The electrode pad in a semiconductor device according to the present invention, which is an end portion of a metallic wiring made of aluminum as a major component and formed on an insulation film of a semiconductor integrated circuit, is characterized in that the exposed surface of the metallic wiring having the periphery surrounded by a protective film comprises a rough surface roughened by means of an etching solution.
According to the electrode pad in a semiconductor device of the present invention, the exposed surface of the metallic wiring, that is, the pad surface is bleached with an etching solution to become a rough surface having a substantially constant roughness. This makes a contribution to enhancement of the adhesion of the bonding wire in contact with the pad.
The method of producing an electrode pad in a semiconductor device according to the present invention by which an end portion of a metallic wiring made of aluminum as a major component formed on an insulation film of a semiconductor integrated circuit is produced, comprises the steps of forming a protective film on the metallic wiring, dry-etching the protective film to form a pad opening so that at least the metallic wiring corresponding to a pad pattern is exposed, and cleaning the exposed surface of the metallic wiring present on the bottom of the pad opening by means of an etching solution. Characteristically, the etching solution is an amine type aqueous solution or a TMAH aqueous solution.
According to the method of producing an electrode pad in a semiconductor device of the present invention, when impurities remaining on the bottom of the pad opening are removed in the cleaning step carried out after the dry-etching step, the roughening of the exposed surface of the metallic wiring by means of an etching solution is also performed.